Fluid flow rate measuring and gas bubble detecting apparatus

ABSTRACT

A fluid flow sensing and bubble detecting apparatus includes a housing comprising a channel configured to receive a tube through which fluid flows; a sensor apparatus disposed within the housing, which includes a first sensor operable to measure flow rate of fluid and to detect bubbles in flowing fluid; and a temperature sensor operable to detect temperature of the flowing fluid; and a processor connected to receive fluid flow rate data obtained by the first sensor, to receive bubble detection data obtained by the first sensor, and to receive fluid temperature data obtained by the temperature sensor, wherein when a tube through which fluid flows is disposed in the channel of the housing, the first sensor measures the flow rate of the flowing fluid and detects bubbles therein, and the temperature sensor measures the temperature of the flowing fluid, and the processor calculates in a short period of time a fluid flow rate corrected for temperature. All sensors are non-invasive and have no direct contact to the fluid in the tube, which might be blood. In accordance with additional embodiments, the fluid flow rate is additionally corrected for hemoglobin or hematocrit, and the effect of oxygen saturation on the hemoglobin or hematocrit data.

FIELD OF THE DISCLOSURE

The field of the present disclosure pertains to that of fluid flow ratesensing apparatuses and bubble detecting apparatuses, such as may beused to determine the flow rate of fluid in a tube or pipe, and whichmay be used to detect gas bubbles in the fluid in the tube or pipe. Morespecifically, the present disclosure pertains to fluid flow ratemeasuring and gas bubble detecting apparatuses, such as operate to bothdetermine the flow rate of a fluid and to detect the presence or absenceof bubbles in a fluid. The present disclosure further pertains to use ofthe aforementioned fluid flow rate measuring and gas bubble detectingapparatuses in one or more systems and medical procedures, includingthose relating to extracorporeal blood circuits and systems, morespecifically cardiopulmonary systems and procedures involving themovement of blood to and/or from the heart via pumps replacing all or aportion of the pumping activity typical of a beating heart (e.g.,cardiopulmonary bypass procedures), or also movement of blood in orderto support/replace the function of the lung whereas the heart is notassisted (e.g. extracorporeal membrane oxygenation systems andprocedures), or other applications where blood is moved (e.g., dialysissystems and procedures).

BACKGROUND OF THE DISCLOSURE

In the health field, medical equipment such as kidney dialysis machines,infusion pump blood analyzers, transfusion systems, cardio-pulmonarybypass/assist machines, and the like, include, or are attached to, tubesin which a patient's blood flows, or in which some form of infusionfluid flows. These fluids flow from these tubes into the patient's bloodstream by means of a cannula, and it is important for patient care, andto ensure patient safety, that the flow rate of the fluid isappropriately monitored. It is also important to measure the temperatureof these fluids entering the patient's body so as not to put unduestress on the patient with infusion of fluids that are substantiallywarmer or colder than target body temperatures, whether physiologic ortherapeutic. In some cases, the infusion of fluids may have a fluidtemperature that is substantially above, or substantially below,physiologic body temperature (e.g., therapeutic cooling during heartsurgery to 18° C. followed by rewarming at the end of surgery). In suchinstances, the need to monitor temperature of the fluids in these casesis greater.

It is also important to monitor fluid flowing in these tubes forundesirably large gas bubbles, whether air or some other gas, becausesuch gas bubbles have the potential to harm the patient as emboli whenthey enter the patient's bloodstream. One solution with respect to themonitoring of fluid flow rate, fluid temperature, and the monitoring forgas bubbles in the flowing fluid, is to provide separate sensors andassociated electronic circuits for each of these parameters, namely,fluid flow rate, fluid temperature, and the presence of substantial gasbubbles. However, a disadvantage to such systems would be theircomplexity of construction, which makes them more costly to manufacture,deploy and maintain.

A partial solution to this problem is disclosed by U.S. Pat. No.7,661,294 B2, issued to Dam, and which is incorporated herein byreference in its entirety. According to this Dam patent, amulti-function sensor system may be constructed with piezoelectricelements that are operated as part of an air bubble detection andcharacterization apparatus. Dam further discloses that themulti-function sensor system includes an infra-red thermocouple employedas a temperature sensor element operated to measure the internaltemperature of liquid in a tube non-invasively by measuring both thetube surface temperature and ambient temperature. The multi-functionsensor system disclosed by Dam includes a force/pressure sensor thataccomplishes non-invasive measurement of internal pressure of an elastictube to detect tube occlusion and/or disconnections.

The Dam patent discloses a liquid color sensing circuit that employs alight emitting element and phototransistor to sense the color of liquidin a tube. However, Dam does not disclose a circuit for detectinghematocrit and/or hemoglobin of blood in a tube. It is known thathematocrit and/or hemoglobin of blood may affect blood flowmeasurements, so there is a need for a blood flow sensing apparatus thatsenses blood flow rate more accurately in a tube or pipe by correctingfor the effect of hematocrit/hemoglobin and/or the effect of temperatureon the blood flow measurements.

There remains a need for a compact, easy to deploy and use apparatusthat senses fluid flow rate and that detects the presence of gas bubblesfor fluid flowing in a tube or pipe. Furthermore, there remains a needfor an apparatus that senses fluid flow rate more accurately thanprevious fluid flow sensing apparatuses.

SUMMARY OF THE DISCLOSURE

An apparatus is disclosed herein that constitutes a fluid flow sensingand bubble detecting apparatus. In accordance with a non-limitingillustrative embodiment of such an apparatus, a fluid flow sensing andbubble detecting apparatus is described that includes (a) a housingprovided with a channel configured to receive a tube through which fluidflows; (b) a sensor apparatus disposed within the housing, wherein thesensor apparatus includes a first sensor operable to measure a flow rateof a fluid, a second sensor operable to detect bubbles in a flowingfluid, and a temperature sensor operable to detect a temperature of aflowing fluid; and (c) a processor operably connected to receive fluidflow rate data obtained by the first sensor, and operably connected toreceive bubble detection data obtained by the second sensor, andoperably connected to receive fluid temperature data obtained by thetemperature sensor. In accordance with this non-limiting embodiment ofthe apparatus, when a tube through which fluid is flowing is disposed inthe channel of the housing, the first sensor measures the flow rate ofthe flowing fluid, and the second sensor detects bubbles in the flowingfluid, and the temperature sensor measures the temperature of theflowing fluid. In accordance with an embodiment of this disclosure, thefluid flow rate data, and the fluid temperature data may be used by theprocessor to calculate a temperature corrected fluid flow rate for thefluid flowing in the tube. Various other non-limiting illustrativeembodiments of the apparatus are also disclosed herein.

A method is disclosed herein that constitutes a method of monitoring afluid flowing through a tube that is a component of medical equipment orthat is connected to medical equipment. Such a non-limiting illustrativeembodiment of such a method comprises the steps of: (a) operating afluid flow sensing and bubble detecting apparatus that comprises asensor apparatus disposed within a housing in order to generate fluidflow rate data and fluid temperature data with respect fluid flowingwithin a tube or pipe, wherein the sensor apparatus includes a firstsensor operable to measure a flow rate of a fluid, a second sensoroperable to detect bubbles in the flowing fluid, and a temperaturesensor operable to measure a temperature of the flowing fluid; and (b)calculating a temperature corrected fluid flow rate from the generatedfluid flow rate data and the fluid temperature data, wherein calculationof the temperature corrected fluid flow rate is performed by a processorof the fluid flow sensing and bubble detecting apparatus. Various othernon-limiting embodiments of the method are also disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fluid flow sensing and bubbledetecting apparatus in accordance with a non-limiting illustrativeinventive embodiment of this disclosure.

FIG. 2 is a schematic illustration of a sensor apparatus of the fluidflow sensing and bubble detecting apparatus of FIG. 1.

FIG. 3 is a schematic illustration of a processor employed to receivedata from sensors of the sensor apparatus of FIG. 2.

FIG. 4 is a schematic illustration of the electronics of a non-limitingillustrative inventive embodiment of a fluid flow sensing and bubbledetecting apparatus of this disclosure.

FIG. 5 is a schematic illustration of the electronics of anothernon-limiting illustrative inventive embodiment of a fluid flow sensingand bubble detecting apparatus of this disclosure.

FIGS. 6A and 6D are schematic illustrations of ultrasonic piezoelectricsensor orientations about a tube or pipe T in accordance withillustrative and non-limiting inventive embodiments of this disclosure.

FIG. 6B is a schematic illustration of ultrasonic piezoelectric sensororientation about a tube or pipe T in accordance with anothernon-limiting inventive embodiment of this disclosure.

FIG. 6C is a schematic illustration of ultrasonic piezoelectric sensororientation about a tube or pipe T in accordance with anothernon-limiting inventive embodiment of this disclosure.

FIG. 7 is a schematic illustration of the electronics of anothernon-limiting illustrative inventive embodiment of a fluid flow sensingand bubble detecting apparatus of this disclosure.

FIG. 8 is a schematic illustration of an extracorporeal blood flowcircuit of a coronary bypass system that employs a fluid flow sensingand bubble detecting apparatus of this disclosure.

FIG. 9 is a schematic illustration of the electronics of anothernon-limiting illustrative inventive embodiment of a fluid flow sensingand bubble detecting apparatus of this disclosure.

FIGS. 10 and 11 are schematic illustrations of the electronics of othernon-limiting illustrative inventive embodiments of a fluid flow sensingand bubble detecting apparatus of disclosure.

FIG. 12 is a schematic illustration of electronics of a blood flowsensing and bubble detecting apparatus in accordance with a non-limitingembodiment of this disclosure.

FIG. 13 is a schematic illustration of a sensor array 600 for measuringblood temperature and hematocrit/hemoglobin that may be used with anultrasonic piezoelectric sensor array 610.

FIG. 14 is a schematic illustration of a sensor array 700 for measuringfluid temperature that may be used with an ultrasonic piezoelectricsensor array 610.

FIG. 15 is a cross-sectional illustration of sensor array 700 formeasuring fluid temperature that may be used with an ultrasonicpiezoelectric sensor array 610.

FIG. 16 is a cross-sectional illustration of a sensor array 800 formeasuring fluid temperature that may be used with an ultrasonicpiezoelectric sensor array 610.

DETAILED DESCRIPTION OF ILLUSTRATIVE, NON-LIMITING INVENTIVE EMBODIMENTS

Various illustrative, non-limiting embodiments of this disclosure aredescribed as follows with reference to the drawings, in which like partsare designated with like character references. First, one or morenon-limiting apparatus embodiments are described, and then one or morenon-limiting method embodiments are described.

FIG. 1 illustrates a fluid flow sensing bubble detecting apparatus 1that includes a main housing 3 provided with a channel 5 configured toreceive a tube T through which fluid F flows. The tube T may beconnected to medical equipment, such as a kidney dialysis machine, aninfusion pump blood analyzer, a transfusion system, an extracorporealmembrane oxygenation (ECMO) machine, or a cardio-pulmonary bypassmachine, or the tube T may be a component of a tubing set connected tosuch medical equipment. The fluid flowing in tube T may, thus, be blood;however, it may also be other kinds of physiologic fluids that includeproteins, electrolytes, volume expanders, etc., which are fluidsinfusible into a patient. Furthermore, the fluid F flowing in the tube Tmay flow in either a forward or backward direction, and the fluid flowsensing and bubble detecting apparatus 1 is able to detect the directionof flow with its flow sensor. Thus, while some figures may show flow inthe forward direction, the fluid flow sensing and bubble detectingapparatus 1 is capable of detecting fluid flow in the reverse direction.

The tube T is preferably clear and/or translucent, and may beconstructed from medical grade tubing such as PVC, silicone,polycarbonate, or other types of medical grade tubing. The apparatus 1may be provided with a cover 7 that is connected by a hinge 9 or otherfastener to the main housing 3 so as to form a clam-shell housing 11that securely fixes the tube T in the channel 5. Because the apparatus 1has a clam-shell housing 11 that clamps onto the tube T, the apparatusmay be characterized as an external clamp-on sensor system that clampsonto the exterior of tube T.

Disposed within the main housing 3 is a sensor apparatus 13, as shown inFIG. 2, that includes a first sensor 15 positioned, and operable, so asto measure or sense a flow rate of the fluid F flowing in the tube T,and a second sensor 17 positioned, and operable, to detect bubbles inthe flowing fluid F, and a temperature sensor 19 positioned, andoperable, so as to measure or sense the temperature of the flowing fluidF. Thus, when tube T through which fluid F is flowing is disposed in thechannel 5 of the main housing 3, the first sensor 15 measures the flowrate of the flowing fluid, and the second sensor 17 detects bubbles inthe flowing fluid, and the temperature sensor 19 measures thetemperature of the flowing fluid. The temperature sensor 19 is capableof measuring the temperature of the fluid whether it is flowing orstanding still (i.e., no flow). The first sensor 15 is a flow sensorthat can detect a no flow state, as well as detect flow in eitherdirection. The second sensor 17 is a bubble detection sensor and canonly detect a bubble if the bubble is moving at a certain minimum speedand has a certain minimum size, although it is not necessary for thefluid to flow for the second sensor 17 to detect bubbles moving in thefluid F.

Because the sensor apparatus 13 includes an array of sensors 15, 17 and19, the sensor apparatus 13 may also be characterized as a sensor array.Optionally, the sensor array may include a sensor for measuring ambienttemperature in addition to, or instead of, the fluid temperaturemeasured by temperature sensor 19. In other words, an ambienttemperature sensor may be employed to provide data used to compensatefor ambient temperature effects on the flowing fluid temperaturemeasurement obtained by the temperature sensor 19. In addition, thelocation and characteristics of temperature sensor 19 permit it tomeasure temperature changes reflecting a steady state more quickly(e.g., on the order of seconds to less than one minute) with respect tofluid F in tube T than in prior art devices in which the steady statefollowing a temperature change may take up to an hour to reachequilibrium as a result of affects caused by the housing of suchdevices.

The apparatus 1 may further include a processor 21 connected to receivefluid flow rate data signal(s) I_(F) provided by the first sensor 15,and connected to receive bubble detection data signal(s) I_(B) providedby the second sensor 17, and connected to receive fluid temperature datasignal(s) I_(T) provided by the temperature sensor 19, as illustratedschematically in FIG. 3. The processor may be located within the mainhousing 3, or the clam-shell housing 11, or the processor may be locatedremotely from the sensor array and in its own separate housing. In thecase when the processor 21 is located remotely from the sensor array, atransmission cable 23 is attached to the main housing 3 and provides atransmission path between the sensor array 13 and the processor 21 overwhich the data signals I_(F), I_(B), I_(T) are transmitted from sensorarray 13 to processor 21. Alternatively, the sensor array 13 may beconnected to a transmitter 24 that is able to transmit the data signalsI_(F), I_(B), I_(T) wirelessly (e.g., via GSM, Bluetooth, WLAN, etc.) toa receiver 25 that is either a part of the processor 21, or operativelyconnected to the processor 21. The processor 21 may also be providedwith a signal processing circuit 26 that processes the signals I_(F),I_(B), I_(T) and outputs processed input to the processor 21. Details ofthe signal processing circuit 26 are provided further below in thisdisclosure.

The processor 21 uses the fluid flow rate data obtained by the firstsensor 15 to calculate the fluid flow rate Q of the fluid F in the tubeT. However, the processor 21 also uses the temperature data obtained bythe temperature sensor 19 to correct the calculated fluid flow rate fortemperature of the fluid. By correcting the calculated fluid flow ratefor the temperature of the fluid F, the calculated flow rate will besubstantially more accurate than calculated fluid flow rates notcorrected for the temperature of the fluid F. Thus, the processor 21employs the fluid flow rate data and the temperature data for the fluidF together to calculate a temperature corrected fluid flow rate Q^(TC)that is desirably more accurate than fluid flow rate computed withoutcorrecting for the temperature of the fluid F. The fact that temperatureof a fluid F may have a substantial effect on flow measurements of thefluid is a known phenomenon as disclosed by G. Poviliunas et al.,Application of Ultrasonic Techniques for Measurement of a Flowrate ofViscous Liquids in a Wide Temperature Range, 3 ULTRAGARSAS 1392-2144(1999), athttp://www.ktu.lt/ultra/journal/pdf_33_3/33-1999-vol.3_04-g.poviliunas.pdf.

Without being limited to a particular theory, the calculation of theflow rate of a fluid is dependent upon its density, which is known tochange with temperature. As an alternative theory, or in additionthereto, temperature influences the speed of ultrasonic signalstraveling in the flowing fluid, which are used to measure flow rates.Therefore, varying temperature of a fluid introduces error into flowmeter measurements of fluid flow. However, temperature correctionfactors for flowing fluids are known and/or are ascertainable withoutundue experimentation. In accordance with the apparatus and methodembodiments described herein, temperature correction of calculated fluidflow rate may be achieved using a propagation time difference methodcorrected for temperature, such as disclosed by U.S. Patent ApplicationPublication No. US 2011/0209558 A1 and U.S. Patent ApplicationPublication No. US 2009/0178490 A1 which are both incorporated herein byreference for all they disclose. Thus, the flowmeter sensor 15 may becharacterized as a transit time flowmeter. However, it is within thescope of this disclosure to employ other suitable models for calculatingfluid flow from one or more ultrasonic signals transmitted through theflowing fluid.

The first sensor 15 that measures fluid flow and generates fluid flowrate data signal(s) I_(F) received by the processor 21 may be embodiedas an ultrasonic flowmeter. In accordance with a non-limiting embodimentof the first sensor 15, the ultrasonic flowmeter includes an ultrasonicpulse emitter-receiver 27, and an ultrasonic pulse emitter-receiver 29that is disposed either upstream or downstream to receive ultrasonicpulses emitted from the ultrasonic pulse emitter 27, and vice-versa, sothat ultrasonic pulses that have traveled transversely at an acute orobtuse angle through the flowing fluid are used by the first sensor 15to generate, in a known manner that requires upstream and downstreamtravel time in order to calculate a time difference that is then usedfor flow calculation, fluid flow rate data corresponding to the fluidflow rate of the flowing fluid. The components 27 and 29 of the firstsensor 15 may be constructed as piezoelectric elements of any suitablematerial, such as lead zirconate titanate (PZT), or modified PZT, orlead-free piezo ceramics, or polyvinylidene difluoride (PVDF) materials.Also, each of the piezoelectric elements 27, 29 are ultrasonictransducers capable of both emitting and receiving ultrasonic signals sothat the piezoelectric elements 27, 29 may each generate fluid flow ratedata while transmitting and receiving in a reciprocal manner with eachother, such as described in U.S. Patent Application Publication No. US2009/0178490 A1 and in U.S. Patent Application No. US 2011/0209558 A1,which are incorporated herein by reference, in order to generate fluidflow rate data signal(s) I_(F).

The second sensor 17 that detects bubbles in the flowing fluid andgenerates bubble detection data signal(s) I_(B) received by theprocessor 21 may be embodied as an ultrasonic detector. In accordancewith a non-limiting embodiment of the second sensor 17, the secondsensor 17 includes an ultrasonic pulse emitter 31, and an ultrasonicpulse receiver 33 that is disposed to receive ultrasonic pulses emittedfrom the ultrasonic pulse emitter 31, so that ultrasonic pulses thathave traveled through the flowing fluid are used by the second sensor 17to generate bubble detection data corresponding to the presence, and/orabsence, of bubbles in the flowing fluid. The components 31 and 33 ofthe second sensor 17 may be constructed as piezoelectric elements of anysuitable material, such as lead zirconate titanate (PZT), or modifiedPZT, or lead-free piezo ceramics, or polyvinylidene difluoride (PVDF)materials, such as disclosed by U.S. Pat. No. 7,661,294 B2, which isincorporated herein by reference. Also, each of the piezoelectricelements 31, 33 may each be ultrasonic transducers capable of bothemitting and receiving ultrasonic signals so that the piezoelectricelements 31, 33 may generate bubble detection data while transmittingand receiving in a reciprocal manner with each other in order togenerate bubble detection data signal(s) I_(B).

The temperature sensor 19 that detects temperature of the flowing fluidand generates fluid temperature data signal(s) I_(T) received by theprocessor 21 may be embodied as a non-invasive, non-contact infra-reddetector (i.e., an infra-red thermometer, such as Melexis MLX90614 orMLX81101) that measures temperature of flowing fluid with an accuracy ofabout ±0.5° C., depending on the type of tube T employed. For example,when the tube T is made of polycarbonate, the non-invasive infra-reddetector (Melexis MLX90614 sensor) measures temperature of the flowingfluid with an accuracy of ±0.5° C. with ambient temperaturecompensation. However, deploying other kinds of tubing T, such assilicone tubing, may affect the accuracy of the infra-red detector sothat the temperature measurements may be less accurate.

The temperature sensor 19 is preferably an infra-red sensor that has nodirect contact with the fluid F, for example blood, flowing in the tubeT. In accordance with another non-limiting embodiment of the temperaturesensor 19, the temperature sensor 19 may constitute a thermocoupleassembly that involves a light emitting element 35, such as a infra-redlight emitting diode (LED), and alight receiving element 37, such as asilicon photo transistor, which is disposed to receive infrared lightemitted from the light emitting element 35. In this alternate embodimentof a non-contact sensor 19, infrared light generated by the LED that hastraveled through the flowing fluid is used by the temperature sensor 19to generate analog fluid temperature data corresponding to thetemperature of the flowing fluid. It is preferable, however, to embodythe temperature sensor 19 as a single, passive infra-red (IR)thermometer detector instead of as an LED 35 and light receiving element37 combination because the single infra-red thermometer detector is apassive sensor that detects IR radiation emitted by the fluid F.Consequently, the infra-red thermometer detector is disposed only on oneside of the tube T, does not emit any light, and employs IR radiationentering the sensor from the tube T to warm a membrane of the infra-redthermometer detector. The temperature of this membrane is measured andcompared to other internal temperatures

One non-limiting example of the signal processing circuit is shown inFIG. 4. The processor 21, which may be a microprocessor, is suitablyprogrammed to perform all of the functions described below. That is, theprocessor 21 outputs the necessary signals to control the operation ofeach of the several sensor elements to perform its intended function andto produce an output measurement. The processor 21 also has an output online 41 that controls operation of a bi-directional multiplexer 43 thatis gated by the processor 21 to sequentially apply the signals from theprocessor 21 to control operation of a fluid flow rate measuring circuit45 associated with offset piezoelectric sensor elements 27 and 29, atemperature measuring circuit 47 associated with infrared sensor element37 (or, alternatively, with an IR thermometer detector such as a MelexisMLX90614 sensor), and an air bubble detection circuit 49 associated withthe piezoelectric sensor elements 31 and 33. The piezoelectric sensorelements 31 and 33 of the air bubble detection circuit 49 may be, but donot have to be, offset in a manner such as described with respect topiezoelectric sensor elements 27 and 29. In other words, piezoelectricsensor elements 27 and 29 may be located directly across from oneanother when tube T is disposed in channel 5 of the housing 3.

An analog to digital converter 51 digitizes analog output signal(s) fromany of the circuits 45, 47 and 49 and applies it to the processor 21 forprocessing for producing the proper output depending upon the sensorelement that is active. The processor 21 is operably connected to drivean audio-visual display apparatus 53 to display measurement results,warnings, and other information, in either solely visual mode, solelyaudio mode, or in a combined audio and visual mode. The processor alsocan produce outputs to other devices 55 such as printers, audio alarms,vibratory alarms, record recording devices, etc.

The fluid flow rate measuring circuit 45 is gated on for operation bythe multiplexer 43 for a predetermined time by the processor 21. Energyin the ultrasonic frequency range, e.g., 2-5 MHz, is supplied by thegenerator 57 to ultrasonic sensor element 27 (or 29) that is to be thetransmitter element to be transmitting to the opposing other ultrasonicsensor element 29 (or 27) serving as the receiver element, and then viceversa. Electronics 59 includes a multiplexer and may be provided with atimer counter, such as disclosed by FIG. 2 of U.S. Pat. No. 5,856,622,which is incorporated herein by reference in its entirety, in order todirect sequential transmission and reception of ultrasonic wave signalsbetween ultrasonic sensor elements 27, 29 based on a clock signal.Electronics 59 receives control signals directly from the processor 21via line 42. Received ultrasonic energy is converted by thepiezoelectric sensor elements. The signal is then processed byelectronics 59 to an analog output voltage that correlates with the timedifference of the ultrasonic signal in and against flow direction. Theanalog output, which may be optionally amplified by an amplifier (notshown) if needed, is applied to the analog digital (A/D) converter 51,and the digital output is input as fluid flow rate data to processor 21for processing with fluid temperature data, and then displayed viadisplay apparatus 53 as temperature corrected fluid flow rate Q_(TC) ofthe flowing fluid F.

The temperature measuring circuit 47 is any suitable conventionalcircuit used to measure temperature based on infrared (IR) energy. Suchcircuits are well known in the art. When gated on by the processor 21through the multiplexer 43, electronics 63 of the temperature measuringcircuit 47 produce an analog output voltage that is amplified by anamplifier 65. The amplified analog output is applied to the analog todigital (A/D) converter 51, and the digital output is input as fluidtemperature data to the processor 21 for processing with fluid flow ratedata as discussed above, and optionally displayed via display apparatus53 as fluid temperature of the flowing fluid F.

In an embodiment of this disclosure, an IR thermometer detector, such asa Melexis MLX90614 sensor, may be employed as temperature sensor 19instead of the LED 35 and light receiving element 37 assembly. In thisembodiment, the IR thermometer (Melexis MLX90614) may input an analogPWM signal to the electronics 63 of the temperature measuring circuit47. However, the Melexis MLX90614 sensor is provided with its owndigital interface (SMBus/“I2C”), so its input into the processor 21 maybe digital, in which case there can be a direct connection between theMelexis MLX90614 sensor and the processor (not gated via themultiplexer). On the other hand, it is also possible to connect thedigital output of the Melexis MLX90614 sensor to the multiplexer 43using a digital-to-analog converter incorporated in the electronics 63,which would allow the electronics 63 to accept a digital input insteadof an analog input.

The air bubble detection circuit 49 is also gated on for operation bythe multiplexer 43 for a predetermined time by the processor 21. Energyin the ultrasonic frequency range, e.g. 2-5 MHz, is supplied by agenerator 67 to ultrasonic sensor element 31 (or 33) that is to be thetransmitter element transmitting to the opposing other element 33 (or31) that is to be serving as the receiver element. The receivedultrasonic energy is amplified in an amplifier 69 and detected andpreferably split by a suitable circuit 71 into a steady state (DC)component and a varying or transient (AC) component, wherein thecomponents respectively are indicative of the absence and the presenceof an air bubble or a particle in the liquid, as described in U.S. Pat.No. 7,661,293 B2, which is incorporated herein by reference in itsentirety. The two components of the signal are applied to the A/Dconverter 51 whose output is supplied to microprocessor 21, which usesthe digital data that corresponds to the presence of a varying transientcomponent to indicate the presence of an air bubble (and/or a particleas well) and to determine its characteristics. The component signals maybe modified to adjust the sensitivity of bubble detection so thatthresholds with respect to bubble size may be selectively set. Inparticular, it is advantageous to provide a gated control of the airbubble detection circuit 49 using the multiplexer 43 to selectively setat least three threshold limits for bubble size detection. When liquidis flowing through the tube T, the presence of the steady-statecomponent of the split signal indicates that the system is operatingproperly to provide a continuous self-check against system malfunction.

The air bubble detection circuit 49 of this disclosure is just oneexample of a suitable air bubble detection circuit. Other circuitssuitable for air bubble detection may be employed in the electronics ofa fluid flow rate measuring and gas bubble detecting apparatus inaccordance with this disclosure, such as in those apparatusesschematically illustrated by FIGS. 4, 5, 7, 9, 10 and 11. In thiscontext, detected bubble size pertains to a cross sectional area of thebubble rather than the volume of the bubble. However, because multiplepiezoelectric sensors in accordance with some embodiments of the sensorarray may detect bubbles along substantially different pathways, andbecause fluid flow rate is measured, bubble detection size may pertainto an estimated volume of a bubble. This improves bubble detectionaccuracy by the processor, which can use both bubble detection data, andbubble flow rate data, to detect bubbles. In accordance with thisdisclosure, the air bubble detection circuit 29 may be constructed tooperate based on an “amplitude drop method,” which sends frequent pulsesin order to monitor continuously the fluid to determine whether bubblesare present or not. According to the amplitude drop method, when thereis a certain threshold drop of the received amplitude of the pulses thatare sent frequently between the piezoelectric sensors, then the circuitconstrues this threshold drop as a detected bubble, and a bubble alarmis activated. In this way, a bubble cannot pass through the fluid flowrate measuring and gas bubble detecting apparatus without beingdetected. Consequently, even if the tube T becomes totally filled withair instead of a fluid F, the bubble alarm gets triggered because thereceived amplitude of the pulses emitted by the piezoelectric sensorsfalls below the minimum threshold. Thus, an air bubble detection circuit49 constructed to operate based on the amplitude drop methodcontinuously monitors the tube T to detect whether there is a bubblepresent or not in the flowing fluid F and it detects whether the tube Tis completely or almost completely filled with air, which is a conditionthat might fool other bubble detection circuits.

Because the sensors 27, 29, 31 and 33 of the fluid flow rate measuringcircuit 45 and the air bubble detection circuit 49 are ultrasonicpiezoelectric sensors, it is possible to employ them for double duty asboth fluid flow rate detection sensors and fluid bubble detectionsensors. As shown in FIG. 5, the circuit of FIG. 4 may be modified toreplace circuits 45 and 49, respectively, with dual fluid flow rate andbubble detection circuits 73, which include a multiplexing circuit 75for multiplexing the data input signals from ultrasonic sensors 27 and29 (or 31 and 33). The multiplexed signals then are used for fluid flowrate measurement using the appropriate fluid flow rate data processingelectronics 61 (which may include a timing circuit, a timing counter,amplifier, etc.), or for fluid bubble detection using the appropriatebubble detection data electronics 69 and 71. In this way, the accuracyof fluid flow rate measurement and of bubble detection is improvedbecause two separate ultrasonic pulse paths are used to generate dataregarding fluid flow rate and the presence (or absence) of bubbles inthe fluid. Furthermore, the ultrasound signal generators 57, 67 of FIG.5 may be embodied as a single generator gated by the multiplexer 43 tosupply energy for the sensor elements of both dual fluid flow rate andbubble detection circuits 73. Multiplexer 75 can direct the electronicsignal from the generator connected to it to any of the piezoelectricsensor elements operably connected to the multiplexer 75. Control of themultiplexer 75, including its timed gating operation, is provided by theprocessor 21. In accordance with another embodiment of this disclosure,the multiplexer 75 may incorporate a timing circuit, such as disclosedby FIG. 2 of U.S. Pat. 5,856,622, which is incorporated herein byreference in its entirety.

As shown in FIGS. 6A and 6B and 6C and 6D, the ultrasonic flow path Abetween sensors 27 and 29, and the ultrasonic flow path B betweensensors 31 and 33, may be located at different height levels spacedlengthwise along the tube T (FIG. 6A) or at different crisscrossinglevels spaced lengthwise along the tube T (FIG. 6B), or at top-bottomand left-right orientations (FIG. 6C) to form a cross, or at the sameheight level spaced lengthwise along the tube T (FIG. 6D). As evidentfrom FIGS. 6A, 6B, 6C and 6D, the ultrasonic sensors 27 and 29, and 31and 33, are paired together so as to send and receive ultrasonic signalsback and forth along paths A and B, respectively, in a manner that istransverse to fluid flow F.

In the embodiment of FIG. 5, temperature data regarding fluid F may beprovided to the circuit of FIG. 5 by a light receiving element 37 asshown in FIG. 4, which is an IR thermocouple generating analog output.Such analog output must be processed by the A/D converter 51 before itis input into processor 21. However, alternatively, the temperature dataregarding the fluid F is preferably provided by an IR thermometerdetector, such as a Melexis MLX90614 sensor, which generates digitaloutput. Such digital output may be input via line 48 to the processor 21without processing by the A/D converter 51 or by any other A/Dconverting circuitry.

In accordance with another non-limiting embodiment, as shown in FIG. 7,only one pair of sensors 27, 29 is required to effect both fluid flowrate measurement and fluid bubble detection. In this case, the sensors27, 29 are located so that the ultrasonic pulse path between the pairedsensors is oriented either horizontally or vertically with respect tothe cross-section of the tube T, and transversely bisects thecross-section of tube T though the center longitudinal axis L of tube Tat either an acute or an obtuse angle. In other words, there must be anon-orthogonal angle between the direction of fluid flow and the path ofthe transmitted ultrasound signals. In this embodiment, the measurementaccuracy of fluid flow rate and the detection accuracy of fluid bubblesmay be less than that of the embodiment of FIG. 5; however, fewerultrasonic piezoelectric sensors are required, which decreasesconstruction costs and permits the construction of a more compact,space-saving fluid flow sensing and bubble detecting apparatus. If thetemperature sensor 19 is an analog sensor, such as an IR temperaturesensor, then its output can be processed by the A/D converter 51. If thetemperature sensor 19 is a digital sensor, such as a Melexis MLX90614sensor, then the digital output may be input to the processor 21 vialine 52.

FIG. 9 schematically illustrates another embodiment of a fluid flowsensing and bubble detecting apparatus in accordance with thisdisclosure. According to the embodiment of FIG. 9, paired piezoelectricsensors 27, 29 are operably connected to provide sensor input and outputto a multiplexing circuit 430, which is connected to provide input,after amplification by an amplifier 436, to a timing circuit 432 of anelectronics circuit 438. The timing circuit 432 comprises a time counteras described with respect to FIG. 2 of U.S. Pat. No. 5,856,622, and thetiming circuit 432 provides digital input to the processor 21 that isused for controlling a time interval between the ultrasonic wavetransmission from one of the paired sensors 27, 29 and the ultrasonicwave reception by the other one of the paired sensors 27, 29, and viceversa. Optionally, a second pair of ultrasonic sensors 31, 33 may beoperably connected to provide sensor input and output as well to themultiplexing circuit 430 in order to determine fluid flow rates. In thiscase, the timing circuit 432 provides digital input to the processor 21that is used for controlling a time interval between the ultrasonic wavetransmission from one of the paired sensors 31, 33 and the ultrasonicwave reception by the other one of the paired sensors 31, 33, and viceversa, and that is also used for gating activation of each sensor pair27, 29 and 31, 33 at different times. A temperature sensor 19, such as aMelexis MLX90614 sensor described above, inputs digital temperature datapertaining to the fluid flowing in the tube T into the processor 21.

Output from the multiplexing circuit 430 is amplified by an amplifier436, and then input into the electronics circuit 438 before a signalprocessed by electronics circuit 438 is input into the processor 21 inorder to determine fluid flow rate of the fluid in the tube T. However,amplified signal from amplifier 436 may also be input into a suitablecircuit 440 that splits the signal into a steady state (DC) componentand a varying or transient (AC) component, wherein the componentsrespectively are indicative of the absence and the presence of an airbubble or a particle in the liquid, as described in U.S. Pat. No.7,661,293 B2, which is incorporated herein by reference in its entirety.The two components of the signal are applied to an A/D converter that isincorporated in the suitable circuit 440 before becoming output suppliedto microprocessor 21, which uses the inputted signal data to indicatethe presence of an air bubble (and/or a particle as well) and todetermine its characteristics.

The processor 21 outputs calculated fluid flow rate data, which may becorrected for temperature of the fluid, and calculated bubble detectiondata, to audio-visual display apparatus 53 and to other devices 55.Processor 21 also has an output on line 441 that controls operation ofthe bi-directional multiplexer 430 that is gated by the processor 21 tosequentially apply the signals from the processor 21 to controloperation of the piezoelectric sensor elements 27 and 29 (and 31 and 33,when present) when operating these sensors to determine fluid flow ratedata and to detect the presence of air bubbles and/or particles.Processor 21 also controls energy in the ultrasonic frequency range,e.g., 2-5 MHz, supplied by the ultrasound generator 442 to ultrasonicsensor element 27 (or 29) that is to be the transmitter element to betransmitting to the opposing other ultrasonic sensor element 29 (or 27)serving as the receiver element, and then vice versa. When multiplepairs of ultrasonic sensor elements are employed, such as paired sensors27, 29 and paired sensors 31, 33, the processor controls the energysupplied to one sensor 27, 31 of each pair so that it acts as anultrasound transmitter while the other member 29, 33 of the pair acts asa receiver, and then the processor controls the energy supplied so theother member 29, 33 of each pair so it serves as the transmitter whilethe sensor 27, 31 of each pair behaves as the receiver.

Because there is only one timer circuit 432, when multiple pairs ofultrasonic elements are employed only one sensor pair is activated at atime to collect fluid flow rate data or bubble detection data. Forexample, using the multiplexer 430, first the sensors 27 and 29 areactivated so that sensor 27 serves as emitter and sensor 29 serves asreceiver, then the multiplexer activates sensors 27 and 29 so thatsensor 29 serves as emitter and sensor 27 serves as receiver, so thatfluid flow rate data is obtained. While sensors 27 and 29 are activated,sensors 31 and 33 are not activated. Subsequently, the multiplexer 430activates sensors 31 and 33, which means that sensors 27 and 29 are notactivated, so that sensor 31 serves as emitter and sensor 33 serves asreceiver in order to obtain fluid flow rate data. Subsequently,multiplexer 430 activates sensor 33 so that it serves as emitter andsensor 31 serves as receiver in order to obtain fluid flow rate data.Afterwards, the multiplexer may activate sensors 31 and 33 in order tocollect bubble detection data, while the sensors 27 and 29 are inactive,and subsequently activate sensors 27 and 29 in order to collect bubbledetection data while sensors 31 and 33 are inactive. Bubble detectiondata may be generated when emitting a signal only in one direction,e.g., from sensor 27 to sensor 29, or from sensor 29 to sensor 27, or inboth directions, e.g., between sensors 27 and 29. Similar patterns ofpiezoelectric sensor activation are employed by the embodiment of FIG.5.

In accordance with this disclosure, following a substantial change intemperature of the fluid flowing in the tube, the processor 21 respondsimmediately (some seconds depending on the flow rate and tube thickness)with the change of the temperature and to calculate the temperaturecorrected fluid flow rate of the flowing fluid. Moreover, a fluid flowsensing and bubble detecting apparatus as disclosed does not require theuse of an ultrasonic transmission gel to operate on a tube or pipe;however, the apparatus may be used with ultrasonic transmission gelapplied to the tube or pipe. Preferably, the tube T is a polyvinylchloride (PVC) tube or a silicone tube; however, the fluid flow sensingand bubble detecting apparatus disclosed herein may be applied to otherkinds of tubes or pipes, such as a thin polycarbonate connector. Inaccordance with this disclosure, the clam-shell housing 11 may beprovided with a push-button operated latching mechanism 79 that latchesthe cover 7 to the main housing 3 to keep the cover 7 in aclosed-position.

FIG. 10 schematically illustrates another embodiment of a fluid flowsensing and bubble detecting apparatus in accordance with thisdisclosure. According to the embodiment of FIG. 10, paired piezoelectricsensors 27, 29 are operably connected to provide signal input and outputto a multiplexing circuit 75 of the dual fluid flow rate and bubbledetection circuit 73, which is connected to provide input into anamplifier 69 and a suitable circuit 71 for providing bubble detectiondata depending upon gating of the multiplexing circuit 75. Analog bubbledetection data is input to the A/D converter 51 before being input tothe processor 121 for the purposes of ascertaining the presence, orabsence, of bubbles in the fluid F.

The paired piezoelectric sensors 27, 29 are also operably connected toprovide signal input and output to the multiplexing circuit 75 in orderto provide analog fluid flow rate data, when gated to do so, that isprocessed by the fluid flow rate data processing circuit 61, whichcomprises a timing circuit and other components that output a digitalsignal that is input to the processor 121 for the purpose ofascertaining the fluid flow rate Q of fluid F. The processor 121 isoperably connected to output the calculated fluid flow rate Q and theresults of bubble detection to an audio-visual display apparatus 53and/or other device 55.

The processor 121 is operably connected to provide control signals tothe generator 57 and to the multiplexing circuit 75, so the processor121 controls operation of the multiplexer and the gating of thepiezoelectric sensors 27, 29 as emitters and receivers, and the gatingof output from the piezoelectric sensors 27, 29 for bubble detection orfor fluid flow rate determination. Optionally, the processor 121 is alsooperably connected to receive digital temperature data directly from adigital temperature sensor, such as a Melexis MLX90614 temperaturesensor, so that the processor 121 may calculate out a temperaturecorrected fluid flow rate Q_(TC) of the flowing fluid F based on thedigital temperature data generated by temperature sensor 19 and thedigitally converted analog fluid flow rate data generated bypiezoelectric sensors 27, 29. The processor 121 is operably connected tooutput the fluid flow rate Q (which is not corrected for temperature) orthe temperature corrected fluid flow rate Q_(TC) to the devices 53and/or 55, depending upon whether the digital temperature sensor isemployed.

FIG. 11 schematically illustrates another embodiment of a fluid flowsensing and bubble detecting apparatus in accordance with thisdisclosure. According to the embodiment of FIG. 11, paired piezoelectricsensors 27, 29 are operably connected to provide signal input and outputto a multiplexing circuit 130, which is connected to provide input to abubble detection circuit 132 as bubble detection data, or input to afluid flow rate determination circuit 134 as fluid flow rate data,depending upon gating of the multiplexing circuit 130. Amplifiers 51 areprovided to amplify analog signals output from the multiplexer 130 toamplified signals before they are input into the bubble detectioncircuit 132 or the fluid flow rate determination circuit 134, each ofwhich may include circuitry to convert the inputted analog signals intodigital signals. The digital outputs from the bubble detection circuit132 and the fluid flow rate determination circuit 134 are input to theprocessor 140 to be used, respectively, to determine the presence orabsence of bubbles and to determine fluid flow rate. Because theprocessor 140 is operably connected to receive fluid temperature datafrom a digital temperature sensor 19, the fluid flow rate determined bythe processor 140 may be a temperature corrected fluid flow rate Q_(TC)of the flowing fluid F.

As shown in FIG. 11, the processor 140 is operably connected via line142 to control operation of the multiplexer 130 and the processor 140 isoperably connected via line 144 to control operation of the ultrasonicgenerator 146, which provides the ultrasonic signal that drives thepiezoelectric sensors 27, 29. Results with respect to the presence orabsence of bubble detection, and with respect to calculatedtemperature-corrected fluid flow rates, are output from the processor140 to the audio-visual display apparatus 53 and/or other device 55.

FIG. 12 illustrates a blood flow sensing and bubble detecting apparatusin accordance with another embodiment of this disclosure. The blood flowsensing and bubble detecting apparatus shown in FIG. 12 employscircuitry similar to that of the apparatus shown in FIG. 9. Thus, adescription of like parts is not repeated for the sake of brevity. Theblood flow sensing and bubble detecting apparatus of FIG. 12 isconstructed for monitoring blood flow in a tube, or disposable incontact with blood, and is provided with a sensor 542 that measures thehematocrit or hemoglobin of blood. It does not matter whether sensor 542is a hematocrit sensor or a hemoglobin sensor because there is awell-known relationship between hematocrit and hemoglobin so it ismathematically straightforward to convert hematocrit data to hemoglobindata, and to convert hematocrit data to hemoglobin data with a certainaccuracy, using processor 21. For example, one commonly employedrelationship for converting hemoglobin to hematocrit is to multiply thehemoglobin value by three to get the hematocrit value, although otherrelationships may be used that take into account additional factors.Flow compensation can thus be achieved by either measuring hemoglobinand/or hematocrit.

Blood viscosity, hemoglobin/hematocrit and/or density are known toaffect blood flow measurements, and blood viscosity and/or density areaffected by blood temperature and blood hematocrit or hemoglobin. Thus,blood flow measuring error related to blood temperature, and/or to bloodhematocrit or hemoglobin, can be corrected by processor 21, which isprogrammed to correct blood flow measurements for the effects of bloodtemperature and/or blood hematocrit or hemoglobin. Hematocrit orhemoglobin data measured by sensor 542, depending upon whether sensor542 is a hemoglobin sensor or a hematocrit sensor, is input to theprocessor 21, which is programmed to correct blood flow measurementsappropriately for hematocrit or hemoglobin level of the flowing blood.Blood temperature data measured by temperature sensor 19 is input toprocessor 21, which is programmed to correct blood flow measurements fortemperature of the flowing blood. Because processor 21 receives datainput from both sensors 19 and 542, the processor 21 can be programmedto correct blood flow measurements for both blood temperature and eitherhematocrit or hemoglobin. Of course, processor 21 may be programmed tocorrect blood flow measurements based on just the blood temperature datainput from sensor 19, or to correct blood flow measurements based onjust hematocrit and/or hemoglobin data input from sensor 542, or it maybe programmed to correct blood flow measurements based on both the bloodtemperature data input from sensor 19 and the hematocrit and/orhemoglobin data input from sensor 542.

The hematocrit/hemoglobin sensor 542 may be constructed as aspectro-photomeric sensor that determines hematocrit or hemoglobin basedon the intensity of the absorption and reflection of light at differentwavelengths because light at different wavelengths are absorbed andreflected in different intensities depending upon the hematocrit valueand hemoglobin value of the blood. For example, sensor 542 may beconstructed from a plurality of light emitting diodes (LEDs) 612, 614,616 and corresponding photodetectors 613, 615, as shown in FIG. 13, orsensor 542 may be a spectrometer used for hematocrit and/or hemoglobinmeasurement. Thus, different wavelengths may be used to measurehematocrit and/or hemoglobin. For example, LED 612 may have a wavelengthof 1385 nm, and LED 614 may have a wavelength of 806 nm. Thephotodetector 613 may be an InGaAs photodetector. The LEDs andphotodetectors are provided with protective windows 620, each with anappropriate wavelength filtering coating. Each of the sensor 19 andphotodetectors 613, 615, and ultrasonic measurement cell 610, areoperably connected to input measured data to processor 21, which may bea component of a printed circuit board 621. The ultrasonic measurementcell 610 corresponds to one of the ultrasonic piezoelectric sensorarrays shown by FIG. 6A, 6B, 6C or 6D.

In accordance with an embodiment of this disclosure, an oxygensaturation sensor may be connected to processor 21 so that oxygensaturation measurements may be used to increase the accuracy of thehematocrit measurement. To measure hematocrit, hemoglobin, oxygensaturation and blood temperature, a MAQUET BMU 40 venous probe or theVenous Probe of MAQUET CARDIOHELP may be connected to providehematocrit, hemoglobin, oxygen saturation and blood temperature datainput to the processor 21. In accordance with another embodiment of thisdisclosure, the LED 616 may have a wavelength of 659 nm and thephotodetector 615 may be a silicon photodetector.

Sensor 19 may be a non-invasive IR-sensor temperature sensor, or it maybe a negative temperature coefficient (NTC) thermistor with YSI400calibration curve (such as when there is a metal well in thedisposable), or other suitable temperature sensor. Sensor 19 may beeither in direct contact with tubing T, or it may be protected againstblood with an IR-window made of a material selected from the groupconsisting of silicon or zinc selenide (ZnSe) or zinc sulfide (ZnS) orother suitable material that is, to a certain extent, transparent forinfrared light.

FIG. 14 is a schematic illustration of a temperature sensor array 700that may be used with an ultrasonic piezoelectric sensor array 610 tomeasure temperature-corrected fluid flow rates. This temperature sensorarray 700 does not employ a hematocrit/hemoglobin sensor, so it isusable with blood and with fluids other than blood. According to theembodiment of temperature sensor array 700, an ultrasonic measurementcell 610 and temperature sensor 19 are operably connected to inputmeasured data to processor 21, which is a component of a printed circuitboard 710, so that blood flow can be calculated and corrected for bloodtemperature, and air bubbles can be detected. The non-invasiveIR-temperature sensor 19 can have direct contact with the fluid, or itcan be protected against dust and moisture with an infrared transparentwindow 622. The infrared transparent window 622 may be made from variousinfrared transparent materials, such as zinc sulfide (ZnS), zincselenium, or silicon.

The non-invasive IR-temperature sensor 19 may be influenced by ambienttemperature in a way that decreases measurement accuracy. In accordancewith an embodiment of this disclosure, the temperature sensor array 700may optionally be provided with an ambient temperature sensor 620, suchas an NTC thermistor or a platinum resistance thermistor (PT100thermistor) or other suitable thermistor, which is operably connected tosend measured ambient temperature data to the processor 21. The ambienttemperature sensor 620 is disposed to measure ambient temperature, andemploys a resistive thermistor, such as an NTC thermistor or PT100thermistor. The processor 21 uses the ambient temperature data measuredby the ambient temperature sensor 620 to adjust blood flow temperaturedata provided by the IR-temperature sensor 19 for ambient temperature,or to adjust temperature-corrected blood flow calculations for ambienttemperature.

The non-invasive IR-temperature sensor 19 measures mostly infrared lightof the tubing T because infrared light emitted by the fluid is mostlyabsorbed by the tubing's wall. Measurement of infrared light of thetubing is affected by the temperature of the tubing T. In order toimprove accuracy of the temperature measurement of the fluid, anadditional temperature sensor 630 may be disposed to measure thetemperature of the wall of the tube T. This temperature sensor 630 maybe a resistive thermistor, such as an NTC thermistor or a PT100thermistor, and is disposed on a thermal conductive part 632 of thehousing 3, which has good thermal conductivity such as may be providedby a metal. Tube wall temperature data measured by temperature sensor630 is input to the processor 21, which uses the tube wall temperaturedata to correct measured values of the fluid temperature for the effectof tube wall temperature, or which uses the tube wall temperature datato adjust the temperature-corrected blood flow calculations fortemperature of the tubing wall.

FIG. 15 is a schematic cross-sectional illustration of temperaturesensor array 700 that is used with an ultrasonic piezoelectric sensorarray 610. This cross-sectional view shows one advantageous non-limitingrelationship between the temperature sensors 19 and 632 and thecompressed tube T filled with fluid F, such as blood, or water, andpossibly some gas. The cover 7 of the housing 3 may be provided with alocking mechanism 779. FIG. 16 is a schematic cross-sectionalillustration of temperature sensor array 800 that is used with anultrasonic piezoelectric sensor array 610. This cross-sectional viewshows one advantageous non-limiting relationship between one or moretemperature sensors 19 and the compressed tube T filled with fluid F,such as blood, or water, and possibly some gas.

In accordance with this disclosure, a non-limiting embodiment pertainingto a method of monitoring a fluid flowing through a tube that is acomponent of medical equipment, or that is connected to medicalequipment, is provided wherein the method includes the steps of: (a)operating a fluid flow sensing and bubble detecting apparatus thatcomprises a sensor apparatus disposed within a housing in order togenerate fluid flow rate data and fluid temperature data with respect tofluid flowing within a tube or pipe, wherein the sensor apparatusincludes a first sensor operable to measure a flow rate of a fluid, asecond sensor operable to detect bubbles in the flowing fluid, and atemperature sensor operable to measure a temperature of the flowingfluid; and (b) calculating a temperature corrected fluid flow rate fromthe generated fluid flow rate data and the fluid temperature data,wherein calculation of the temperature corrected fluid flow rate isperformed by a processor of the fluid flow sensing and bubble detectingapparatus. According to this method, the calculated temperature has anaccuracy of about ±0.5° C., and the processor calculates a temperaturecorrected fluid flow rate immediately (some seconds to about 20 seconds)following a substantial change in temperature of the fluid flowing inthe tube, although the temperature corrected fluid flow rate calculatedimmediately after the temperature change may not represent a steadystate, and it may take more time to reflect a steady state following thetemperature change. Furthermore, this method may further include thestep of: (c) detecting the presence of one or more gas bubbles in thefluid flowing within the tube or pipe, wherein the second sensor detectsthe one or more gas bubbles. In addition, the first sensor measures theflow rate of the fluid flowing within the pipe or tube, and thetemperature sensor measures the temperature of the fluid flowing withinthe pipe or tube.

However, it is possible for the first sensor to measure both the flowrate of the fluid flowing within the pipe or tube, and also detect thepresence (or absence) of bubbles in fluid flowing within the pipe ortube, when the first sensor constitutes a pair of offset ultrasonicpiezoelectric detectors, or even two or more pairs of ultrasonicpiezoelectric sensors. In this context, a pair of offset ultrasonicpiezoelectric detectors constitutes two ultrasonic piezoelectricdetectors arranged on the exterior of the tube T so there is anon-orthogonal angle between the direction of fluid flow and the path(s)of the transmitted ultrasonic signals. Thus, in accordance with anothernon-limiting method embodiment, a method of monitoring a fluid flowingthrough a tube that is a component of medical equipment, or that isconnected to medical equipment, is provided wherein the method includesthe steps of: (a) operating a fluid flow sensing and bubble detectingapparatus that comprises a sensor apparatus disposed within a housing inorder to generate fluid flow rate data and fluid temperature data withrespect to fluid flowing within a tube or pipe, wherein the sensorapparatus includes a first sensor operable in a first mode to measure aflow rate of a fluid and operable in a second mode to detect bubbles inthe flowing fluid, and a temperature sensor operable to measure atemperature of the flowing fluid; and (b) calculating a temperaturecorrected fluid flow rate from the generated fluid flow rate data andthe fluid temperature data, wherein calculation of the temperaturecorrected fluid flow rate is performed by a processor of the fluid flowsensing and bubble detecting apparatus. According to this method, thecalculated temperature has an accuracy of about ±0.5° C., and theprocessor calculates the temperature corrected fluid flow rateimmediately (some seconds to about 20 seconds) following a substantialchange in temperature of the fluid flowing in the tube. As discussedabove, the calculated temperature corrected fluid flow rate obtainedimmediately after the temperature change may not correspond to a steadystate, so it may take a longer period of time for the calculatedtemperature corrected fluid flow rate to reflect a steady state afterthe temperature change. Furthermore, this method may further include thestep of: (c) detecting the presence of one or more gas bubbles in thefluid flowing within the tube or pipe, wherein the first sensor detectsthe one or more gas bubbles. In addition, the first sensor measures theflow rate of the fluid flowing within the pipe or tube, and thetemperature sensor measures the temperature of the fluid flowing withinthe pipe or tube.

Another non-limiting method embodiment of this disclosure pertains to amethod of monitoring blood flowing through a tube or disposable that isa component of medical equipment or that is connected to medicalequipment, wherein the method comprises the steps of: (a) operating ablood flow sensing and bubble detecting apparatus that comprises asensor apparatus disposed within a housing in order to generate bloodflow rate data and blood temperature data and blood hematocrit orhemoglobin data, and optionally also oxygen saturation data, withrespect to blood flowing within a tube or pipe, wherein the sensorapparatus includes a first sensor operable to measure a flow rate ofblood and to detect bubbles in the flowing blood, and a temperaturesensor operable to measure a temperature of the flowing blood, and ablood sensor operable to measure hematocrit or hemoglobin in the flowingblood; and (b) calculating a corrected blood flow rate from thegenerated blood flow rate data and the blood temperature data and theblood hematocrit or hemoglobin data, wherein calculation of thecorrected blood flow rate is performed by a processor of the fluid flowsensing and bubble detecting apparatus, wherein the corrected blood flowrate is corrected for blood temperature, or blood hematocrit orhemoglobin, or both blood temperature and blood hematocrit orhemoglobin. Furthermore, this method may further include the step of:(c) detecting the presence of one or more gas bubbles in the bloodflowing within the tube or pipe, wherein the first sensor detects theone or more gas bubbles. In accordance with another embodiment of thisdisclosure, these method embodiments may involve calculation of thecorrected blood flow rate in a manner that employs oxygen saturationdata measured by the blood sensor so that the corrected blood flow rateis compensated for the affect of oxygen saturation on the bloodhematocrit or hemoglobin data.

One non-limiting application of a fluid flow sensing and bubbledetecting apparatus, such as described above, is in an extracorporealblood flow circuit 81 of a coronary bypass system, such as is usedduring coronary bypass surgery. The blood flow circuit 81 of thecoronary bypass system of FIG. 8 includes surgical tubing 83 constructedof materials suitable for transporting blood, and optionally coated withmaterials to prevent blood from clotting, which connects the venoussystem V of a patient to the arterial system A of the patient. It shouldbe noted that while a patient is referenced in various embodiments, anon-human patient or patient simulator such as a practice mannequin maybe interchangeably used in place of a human patient. The blood flowcircuit 81 further includes a venous hardshell reservoir 85 for venousblood, and a centrifugal pump 87 that draws venous blood from thereservoir 85 and pumps it through an oxygenator 89, which increases theoxygen content of the blood. The blood flow circuit 81 also includes anarterial filter 91, which filters blood oxygenated by oxygenator 89before it returns to the arterial system of the patient. The blood flowcircuit 81 further includes two fluid flow sensing and bubble detectingapparatuses 1 clamped to the exterior of tubing 83 to measure blood flowrate, detect bubbles in the blood, and measure the temperature of bloodleaving the patient on the venous side and entering the patient on thearterial side. Each of the fluid flow sensing and bubble detectingsensor arrays 13 are connected by transmission lines 23 to anaudio-visual display apparatus 53 and/or other display device 55 so thatfluid temperature, temperature corrected fluid flow rates Q_(TC) andbubble detection results can be displayed. In this way, the bloodflowing in the blood flow circuit 81 may be monitored for its rate offlow, temperature and the presence of air bubbles, which facilitatesoperation of the blood flow circuit 81 of the coronary bypass system bya clinical perfusionist during coronary bypass surgery, therebyimproving patient care.

While the present disclosure describes various inventive embodimentsand/or examples, it is not intended that these embodiments limit thescope of the invention, as it is defined by the appended claims. Forexample, while an embodiment of a fluid flow sensing and bubbledetecting apparatus has been described with application to a coronarybypass system, such an embodiment is not limited to application to acoronary bypass system. Such a fluid flow sensing and bubble detectingapparatus may be applied to other systems through which a patient'sblood flows through tubing, such as a dialysis system, and ECMO system,and the like. Furthermore, such a fluid flow sensing and bubbledetecting apparatus may be applied to systems that do not involve theflow of blood, such as through cell culturing systems in which cellculture medium flows through tubing at a desired rate, temperature andbubble free, or in food processing systems in which fluid flows througha tube at a desired flow rate and temperature, and monitored for thepresence of bubbles, or in a chemical processing system in which variousreaction substrates flow in a liquid medium though a tube at a desiredflow rate and temperature and monitored for the presence or absence ofbubbles.

Moreover, the embodiment of a fluid flow sensing and bubble detectingapparatus illustrated in FIG. 5 may be modified to include thepiezoelectric sensors 27, 29, 31 and 33, the two dual fluid flow rateand bubble detection circuits 73, and no temperature measuring circuit47 and no temperature sensor 19 or infrared sensor element 37 inaccordance with another non-limiting embodiment. Similarly, theembodiment of a fluid flow sensing and bubble detecting apparatusillustrated in FIG. 7 may be modified to include piezoelectric sensors27, 29, one dual fluid flow rate and bubble detection circuit 73, and notemperature measuring circuit 47 and no temperature sensor 19 orinfrared sensor element 37.

In accordance with another non-limiting embodiment, the multiplexer 43,the A/D converter 51, and circuits 45, 47, and 49 are included ascomponents of the signal processing circuit 26, and are housed with theprocessor 21 and not within the clam-shell housing 11 with the sensors27, 29, 31, 33 and 37. On the other hand, in accordance with anothernon-limiting embodiment, the multiplexer 43, the A/D converter 51, andthe circuits 45, 47, and 49 are housed with the sensors 27, 29, 31, 33and 37 in the clam-shell housing 11.

The embodiments of FIGS. 4 and 5 employ two pairs of piezoelectricsensors 27, 29 and 31, 33. However, additional embodiments of fluid flowsensing and bubble detecting apparatuses, in accordance with thisdisclosure, may include more than two pairs of piezoelectric sensors.For example, it is within the scope of this disclosure to modify theembodiments corresponding to FIGS. 4 and 5, respectively, so that eachemploys three pairs of piezoelectric sensors, or four pairs ofpiezoelectric sensors, or five pairs of piezoelectric sensors, or sixpairs of piezoelectric sensors, etc. The additional pairs ofpiezoelectric sensors may be used, in accordance with a modifiedembodiment of FIG. 4, as all additional bubble detecting sensors, or asall additional flow rate measuring sensors, or some of the additionalpaired piezoelectric sensors may be used for bubble detection and someof the additional paired piezoelectric sensors may be used for flow ratedetermination. So, for example, the embodiment of FIG. 4 may be modifiedto employ four pairs of piezoelectric sensors, wherein one pair 27, 29is used for fluid flow rate measuring and one pair 31, 33 is used forbubble detection, and either the remaining two pairs are both used forflow rate measuring, or are both used for bubble detection, or one isused for flow rate measuring and one is used for bubble detection. Inaccordance with a modified embodiment of FIG. 5, all of the additionalpaired piezoelectric sensors may be used as dual use flow rate measuringand bubble detecting sensors, whether the modified embodiment employsthree pairs of piezoelectric sensors, or four pairs of piezoelectricsensors, or five pairs of piezoelectric sensors, or six pairs ofpiezoelectric sensors, etc.

While this disclosure provides multiple exemplary embodiments, it willbe understood by those skilled in the art that various changes may bemade and equivalents may be substituted for elements thereof withoutdeparting from the scope of this disclosure. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of this disclosure without departing from the essentialscope thereof. Therefore, it is intended that the invention, as definedin the appended claims, not be limited to any particular embodimentdisclosed herein, but that the invention will include all embodimentsfalling within the scope of the claims. Also, in the drawings and thedescription, there have been disclosed exemplary embodiments and,although specific terms may have been employed, they are unlessotherwise stated used in a generic and descriptive sense only and notfor purposes of limitation. Moreover, the use of the terms first,second, etc. do not denote airy order or importance, but rather theterms first, second, etc. are used to distinguish one element fromanother. Furthermore, the use of the terms a, an, etc. do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced item unless otherwise explicitly indicated.

1-18. (canceled)
 19. A fluid flow sensing and bubble detectingapparatus, comprising: a housing provided with a channel configured toreceive a tube through which fluid flows; a sensor apparatus supportedby the housing, wherein the sensor apparatus includes a first sensoroperable to measure a flow rate of fluid and operable to detect bubblesin flowing fluid; and a temperature sensor operable to detect atemperature of the flowing fluid; and a processor operably connected toreceive fluid flow rate data obtained by the first sensor, and operablyconnected to receive bubble detection data obtained by the first sensor,and operably connected to receive fluid temperature data obtained by thetemperature sensor, wherein when a tube through which fluid is flowingis disposed in the channel of the housing, the first sensor measures theflow rate of the flowing fluid and detects bubbles in the flowing fluid,and the temperature sensor measures the temperature of the flowingfluid.
 20. The apparatus of claim 19, further comprising: a secondsensor operable to measure the flow rate of fluid and operable to detectbubbles in the flowing fluid, wherein the second sensor is operablyconnected to the processor so the processor receives fluid flow ratedata and bubble detection data obtained by the second sensor so thatwhen the tube through which fluid flows is disposed in the channel ofthe housing, the processor receives fluid flow rate data obtained by thefirst sensor and fluid flow rate data obtained by the second sensor, andthe processor receives bubble detection data from the first sensor andbubble detection data from the second sensor.
 21. The apparatus of claim20, wherein the processor calculates a temperature corrected fluid flowrate of the flowing fluid in the tube based on the fluid flow rate dataobtained by the first sensor, and the fluid flow rate data obtained bythe second sensor, and the fluid temperature data obtained by thetemperature sensor, and the processor outputs the calculated temperaturecorrected fluid flow rate to a display apparatus.
 22. The apparatus ofclaim 20, wherein the processor employs bubble detection data receivedfrom the first sensor and bubble detection data received from the secondsensor to determine whether a bubble is present in the fluid flowing inthe tube.
 23. A method of monitoring a fluid flowing through a tube thatis a component of medical equipment or that is connected to medicalequipment, wherein the method comprises the steps of: operating a fluidflow sensing and bubble detecting apparatus that comprises a sensorapparatus disposed within a housing in order to generate fluid flow ratedata and fluid temperature data with respect to fluid flowing within atube or pipe, wherein the sensor apparatus includes a first sensoroperable to measure a flow rate of a fluid and to detect bubbles in theflowing fluid, and a temperature sensor operable to measure atemperature of the flowing fluid; and calculating a temperaturecorrected fluid flow rate from the generated fluid flow rate data andthe fluid temperature data, wherein calculation of the temperaturecorrected fluid flow rate is performed by a processor of the fluid flowsensing and bubble detecting apparatus.
 24. The method of claim 23,further comprising the step of: detecting the presence of one or moregas bubbles in the fluid flowing within the tube or pipe, wherein thefirst sensor detects the one or more gas bubbles. 25-35. (canceled) 36.The apparatus of claim 19, wherein the first sensor comprises a pair ofultrasonic pulse emitter-receivers disposed to emit and receiveultrasonic pulses from each other, wherein in a first mode of operationthe first sensor generates the bubble detection data from the ultrasonicpulses emitted from the pair of ultrasonic pulse emitter-receivers andin a second mode of operation the first sensor generates the flow ratedata from the ultrasonic pulses emitted from the pair of ultrasonicpulse emitter-receivers, wherein the bubble detection data and the flowrate data are sent to the processor.
 37. The apparatus of claim 19,wherein the temperature sensor comprises a non-invasive/non-contactinfrared temperature sensor that measures temperature of fluid, whetherflowing or standing, with an accuracy of about ±0.5° C.
 38. Theapparatus of claim 1, wherein the processor employs the fluid flow ratedata and the fluid temperature data to calculate a temperature correctedfluid flow rate of the flowing fluid in the tube.
 39. The apparatus ofclaim 38, wherein following a substantial change in temperature of thefluid flowing in the tube, within about a minute the apparatus is ableto calculate the temperature corrected fluid flow rate of the flowingfluid at a new steady state.
 40. A fluid flow sensing and bubbledetecting apparatus, comprising: a housing provided with a channelconfigured to receive a tube through which fluid flows; a sensorapparatus supported by the housing, wherein the sensor apparatusincludes a sensor operable to measure a flow rate of fluid and operableto detect bubbles in flowing fluid; and a processor operably connectedto receive fluid flow rate data obtained by the sensor, and operablyconnected to receive bubble detection data obtained by the sensor,wherein when a tube through which fluid is flowing is disposed in thechannel of the housing, the sensor measures the flow rate of the flowingfluid and detects bubbles in the flowing fluid.